A digital camera hangs over every classroom here, silently recording students' and teachers' every move. The surveillance system is at the leading edge of a trend to equip U.S. public schools with the same cameras that Wal-Mart stores use to catch thieves..Fearful of violence, particularly in light of America's history of schoolhouse shootings, educators are rushing to install ceiling-mounted cameras in hallways, libraries and cafeterias. But no other district has gone as far as this community, which, flush with casino revenue, has hung the cameras not only in corridors and other common areas but also in all of its 500 classrooms..That has made virtually everything that happens at any of Biloxi's 11 public schools subject to instant replay. So far, principals report, they have used such replays to solve only humdrum problems like clarifying the disappearance of a child's ice cream money or ensuring that students do not sleep in class.."It's like truth serum," said Laurie Pitre, principal of North Bay Elementary, who frequently peeks in on her classrooms from a computer monitor in her office. "When we have a he-said, she-said situation, nine times out of 10 all we have to do is ask children if they want us to go back and look at the camera, and they 'fess up.".Pitre and other administrators said the classroom cameras, which Biloxi started phasing in two years ago, had helped improve discipline and, as a result, raise test scores, a view also voiced by some teachers, parents and students. But teachers' unions and civil libertarians have called Biloxi's system an Orwellian intrusion.."Putting cameras on children trains them to believe that being watched every minute of the day is O.K., that Big Brother is O.K.," said Steve Lilienthal, a director at the Free Congress Foundation, a research group based in Washington. "They should be teaching them to behave not because a camera is on them, but because it's the right thing to do.".The Biloxi school district is not the only one where surveillance cameras are provoking controversy. In January, cameras at a school in Livingston, Tennessee, recorded 10- to 14-year-old boys and girls undressing in adjacent changing areas in preparation for basketball, and stored the images on a computer accessible through the Internet, according to a federal lawsuit filed by parents..William Needham, the director of schools in Livingston, said in an interview that the camera system had been installed in a utility room that was later converted to a locker area, and that after the incident he removed it and delivered the images to law enforcement authorities. But the plaintiffs accuse school officials of "callous indifference" to the children's privacy..In many towns, though, cameras are becoming a routine schoolhouse fixture, installed above drinking fountains and laboratory tables, with little or no public notice. No specific laws appear to regulate their use in schools, some of which, as in Canton, Mississippi, are financing their purchase with federal money..When officials are drawing up plans for schools, "there's not one that doesn't want cameras," said Todd Walker, chief financial officer of CameraWatch, a company that has installed surveillance equipment in schools from North Carolina to California..About 950 new public schools opened across the United States in 2002, and school architects estimate that three-quarters were equipped with surveillance cameras..School administrators are enthusiastic because digital technology makes the cameras far easier to use than the analog cameras that recorded images to videotape when educators first began experimenting with surveillance a decade ago. Today's digital cameras use computer hard drives, allowing school principals to conduct a replay of a cafeteria food fight at the click of a mouse..Most districts install cameras only in interior common areas such as hallways and in parking lots, said Greg Chase, technology director for SHW, a Dallas-based architectural firm that specializes in schools. Many districts deem cameras too invasive for classrooms, he said, and in any case the costs can be prohibitive..Civil libertarians and many educators have expressed outrage over Biloxi's surveillance experiment.."I shuddered," said Paul Abramson, a school-design consultant in Larchmont, New York. "Kids are kids. What are we telling them when we put them under surveillance?".Lee Tien, a lawyer for the Electronic Frontier Foundation, which monitors legal issues related to technology, called the Biloxi experiment "a Kafkaesque civil liberties nightmare.".But Allison Buchanan, head of the parent-teacher association at North Bay Elementary, said, "In my two years on the PTA, I've not heard one parent say anything bad about the cameras."